Browsing by Author "Woldeyesus, Mideksa"

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    Mounting Plate, Stress Concentration and Damage Tolerance Analysis for Antenna Installations on Pressurized Transport Aircraft Using The FEM
    (Addis Ababa University, 2021-07) Woldeyesus, Mideksa; Behailu, Mamo (Mr.)
    During the in-service life of a given aircraft, different antennas are installed on the fuselage of the aircraft for different operational and regulatory requirements. These antennas are part of the Communication, Navigation and surveillance (CNS) systems of aircraft. Antennas play the greatest role in enhancing the operational safety and functionality of a given civil or military aircraft by providing reliable communication and navigation systems. During antenna installation, the fuselage skin loses its structural integrity. Taking this into consideration and also fracture mechanics as a basic principle, damage tolerance analysis for antenna installations on pressurized transport airplanes has been studied. For skin modifications, first from a static strength point of view, the elliptical antenna mounting plate is compared with those of circular and rectangular mounting plates. Next, based on the first result, from the stress concentration factor point of view, the best antenna cut-out shape was studied by comparing antenna cut-out shapes such as elliptical, circular, and square cut-outs for mounting plates subjected to biaxial loads. Then, considering the best mounting plate shape and antenna cut-out, i.e., having the lowest stress concentration factor, damage tolerance analysis (DTA) is done using Linear Elastic Fracture Mechanics (LEFM) and the establishing inspection type and inspection threshold are studied. To perform the above activities, a special tool, Finite Element Analysis (FEA), i.e., ANSYS application software, was used to perform static and fatigue simulations along the potential crack growth path for a flaw initiating from the antenna cut-out normal to the stress application direction. The output from finite element modelling and analysis is compared with the analytical for the safe installation of the antenna. With respect to the above framework, the study was done, and the result shows that the circular mounting plate is relatively better than those of the rectangular mounting plate and the elliptical mounting plate. With regard to the cut-out shape, for the applied biaxial tension loads, a circular cut-out is relatively better than those of the square and elliptical cut-out shapes. A circular mounting plate with a circular antenna cut-out is better than an elliptical or rectangular mounting plate. Starting with the initial crack length of a i and the progressive crack length of a i+1 to the critical crack length value ac, which is calculated using the fracture toughness of the skin materials, an estimated inspection type and inspection threshold (damage detection) were established.